1. Field of the Invention
The present invention relates to an infrared light detector.
2. Description of the Related Art
There has been disclosed an infrared light detector by the inventors of the present application using the phenomenon described in, for example, published PCT international application WO2006/006469A1, “Infrared phototransistor using capacitively coupled two-dimensional electron gas layers” (An et al.) Appl. Phys. Lett., 86, 172106(2005), and “A sensitive double quantum well infrared phototransistor” (An et al.) J. Appl. Phys., 100, 044509(2006). Specifically, by a microstrip antenna or the like, a ray of infrared light is concentrated on a two-dimensional electronic layer, such as a quantum dot or the like, which is electrically isolated from the ambient. As a result, a vertical oscillating electric field is generated in the isolated two-dimensional electronic layer. Thereafter, an electron in the isolated two-dimensional electronic layer is excited by the oscillating electric field a ground sub-band level to an excited sub-band level and then escapes from the isolated two-dimensional electronic layer to a source electrode or the like in a charge sensitive transistor disposed underneath the isolated two-dimensional electronic layer. Thereby, the isolated two-dimensional electronic layer becomes positively charged. The electrical charge of the isolated two-dimensional electronic layer increases gradually as the number of electrons escaped from the isolated two-dimensional electronic layer increases gradually, and resultantly, the electrical conductivity of the charge sensitive transistor increases.
When a single infrared light photon is introduced into the antenna, the infrared light detector using the above-mentioned phenomenon can detect the infrared light with a high sensitivity on the basis of the current variation of a charge sensitive transistor.
However, in the infrared light detector, the current variation amount of the charge sensitive transistor becomes saturated in a relatively short time after the detection of the infrared light is initiated, therefore, it has been proved that there is a limit on infrared light sensitivity.